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Pre-installation continued-
SYSTEM ZONE CONTROL
The indirect-fired water heater must be installed as a zone separate
from the space heating system. The domestic hot water zone's
piping and circulator must be sized for a minimum flow rate with all
zones in use and a maximum flow rate with only the water heater in
use. For this reason, the preferred method of zone control is with
circulators.
1. Circulators – With space heating zones using circulators, the
indirect-fired heater should be added as an additional zone with a
circulator.
2. Zone Valves – Select a valve with a low-pressure drop to assure
adequate flow through the water heater.
3. Hybrid – The space heating zone can be zoned using zone
valves and the indirect-fired heater zoned with a circulator.
DOMESTIC HOT WATER PRIORITY
Two options are available, Priority and Non-Priority.
1. Priority – Demand for space heating is interrupted or postponed
until the domestic hot water demand is satisfied. This option
provides maximum delivery of domestic hot water. Priority is
recommended when:
a) Boiler net output is 100,000 Btu per hour or less, or
b) When boiler output required to satisfy domestic hot water
demand is at least 50% of the boiler output required to satisfy
space heating demand, or
c) When an interruption in space heating can be tolerated during
a long domestic hot water draw.
2. Non-Priority – Boiler output is divided between space heating
and domestic hot water heating. Delivery of domestic hot water
can be reduced during simultaneous space and domestic hot
water heating operations, depending on such factors as boiler
output, boiler over-sizing, number of space heating zones calling
for heat, and the ratio of domestic hot water load to space
heating load.
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